{
 "metadata": {
  "date": "2014/03/10",
  "name": "The Terror of Subtraction",
  "signature": "sha256:b44a33049de49d343e974afaf61f205f529a2575e13a2aa178fc2b30464dbed8"
 },
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 "worksheets": [
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     "cell_type": "markdown",
     "metadata": {},
     "source": [
      "The subtraction operation is disturbing because,\n",
      "even if carefully fed only positive integers,\n",
      "it can produce an answer outside of that domain:"
     ]
    },
    {
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     "input": [
      "6 - 7"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "metadata": {},
       "output_type": "pyout",
       "prompt_number": 1,
       "text": [
        "-1"
       ]
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    }
   ],
   "metadata": {}
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}